Abstract
Dental caries is caused by acids released from bacterial biofilms. However, the in vivo formation of initial biofilms in relation to caries remains largely unexplored. The aim of this study was to compare the oral microbiome during the initial phase of bacterial colonization for individuals with (CC) and without (NC) cavitated dentin caries lesions. Bovine enamel slabs on acrylic splints were worn by the volunteers (CC: 14, NC: 13) for in situ biofilm formation (2 h, 4 h, 8 h, 1 ml saliva as reference). Sequencing of the V1/V2 regions of the 16S rRNA gene was performed (MiSeq). The relative abundances of individual operational taxonomic units (OTUs) were compared between samples from the CC group and the NC group. Random forests models were furthermore trained to separate the groups. While the overall heterogeneity did not differ substantially between CC and NC individuals, several individual OTUs were found to have significantly different relative abundances. For the 8 h samples, most of the significant OTUs showed higher relative abundances in the CC group, while the majority of significant OTUs in the saliva samples were more abundant in the NC group. Furthermore, using OTU signatures enabled a separation between both groups, with area-under-the-curve (AUC) values of ~0.8. In summary, the results suggest that initial oral biofilms provide the potential to differentiate between CC and NC individuals.
Highlights
Dental caries is a major health problem
NC individuals presented no open decayed surfaces whereas cavitated caries (CC) individuals had a mean of 4.4 ± 1.8 cavitated carious surfaces reaching into the dentin
The identified operational taxonomic units (OTUs) were derived from members of the Proteobacteria (28%), Bacteroidetes (15%), Firmicutes (15%), Actinobacteria (10%), Fusobacteria (3%), Candidatus Saccharibacteria (2%), and Parcubacteria (2%) with other phyla covering less than 2% of the remaining OTUs according to taxonomic assignments created by LotuS
Summary
Dental caries is a major health problem. Recent data demonstrate its high relevance for both the global prevalence of chronic asymptomatic caries as well as for the incidence of acute-caries associated tooth pain[1,2]. Biofilm in situ models offer a promising and standardizable option for obtaining biofilm samples over strictly defined periods of time[7,13] These in situ models can be used to investigate initial bioadhesion processes, basic microbiological and molecular genetic questions, as well as the influences of food and oral hygiene products[13,14,15]. Only few recent studies have characterized the microbiome during initial bacterial colonization in healthy adults in vivo or in situ using high-throughput sequencing approaches[40,41,42]. The aim of the present study was to evaluate and to compare the microbiome of the initial phase of bacterial colonization on an in situ enamel biofilm model systematically after 2 hours, 4 hours and 8 hours for young adults with and without cavitated caries for the first time
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